Dart 2 migration guide for web apps

This page has information on migrating your Dart 1.x web app to Dart 2. These changes are necessary because of the following:

Tooling changes:
- Chrome replaces Dartium and content-shell.
- A new build system replaces pub build, pub serve, pub transformers.
Dart 2 language and library changes.

Tools

The development environment for web apps is different in Dart 2 from Dart 1.x. Here are the highlights:

Dart 1.x	Dart 2
Dartium, content shell	Chrome and dartdevc
`pub build`	`webdev build`
`pub serve`	`webdev serve`
`pub run angular_test`	`pub run build_runner test — -p chrome`. See: Running tests
pub transformers	build package transformers. See: Transforming code

To migrate to Dart 2, you’ll need to edit your web app’s project files:

pubspec.yaml, see details below.
HTML files with <script src="foo.dart"...> elements, such as web/index.html. See details below.
Dart code, due to changes in the Dart language and libraries.

For complete examples of migrated apps, compare the 4.x and master branches of any one of the angular-examples apps, such as these:

Make these changes to your pubspec.yaml file:

Add new dev_dependencies:
- build_runner:
- build_test: , if you are running tests
- build_web_compilers:
Drop dev_dependencies:
- browser
- dart_to_js_script_rewriter
Upgrade to test version 0.12.30 or later; it runs Chrome tests headless by default.
Drop all transformers:
- angular
- dart_to_js_script_rewriter
- test/pub_serve

For example, here is a diff of angular-examples/quickstart/pubspec.yaml with these changes applied.

The most common example of a file with <script> elements is web/index.html. You’ll need to make these changes:

Drop <script defer src="packages/browser/dart.js"></script>
Replace <script defer src="foo.dart" type="application/dart"></script> by
<script defer src="foo.dart.js"></script>

Here is a diff of angular-examples/quickstart/web/index.html with these changes applied.

Dart 2 Updates: Information about changes in Dart 2, and how to migrate your code from Dart 1.x.
Changelog: Lists changes made to this site’s documentation and examples.